Done about a third of a job Squeal shims stuck to the pads are steel and won't cut with a Stanley knife, so cleaned off all the copper slip apart from the guide rail contact and chamfered the leading edge of the pads.
If they still squeal, I will run a disk cutter across the shim steel to score and brake off at an angle.
Not got any RTV of a high enough temp rating to bother using at the moment.